Seriously. It's become an insidious part of teen culture that you should address.

Parents have always struggled with how to talk with their kids about sex, but in a world where pornography is a mouse click away, the conversation is more complicated than ever. A rather alarming number of adolescents — girls as well as boys — seem to be looking at porn online and using it as inspiration for their own sexting, blithely sending explicit pictures of themselves to their crushes and posing suggestively on Snapchat and Instagram.

This state of affairs suggests that some teens may feel that they’re expected to have sexual experience at an early age — because everyone else does. Here’s where you come in. You can be the reality check for your kid.

In fact, although sexting is rampant among the young, sex is not. Although seven in 10 teens have had sex by the time they’re 19, only 13 percent have had sex by age 15. The average age for first intercourse is 17. And 72 percent of girls and 56 percent of guys have sex for the first time with a boyfriend or girlfriend — that is, in some kind of relationship, not in a casual hook-up.

So, if your daughter or son thinks the racy posturing of their peers indicates advanced experience, they are likely to be mistaken. Teens — especially younger teens — need to know that it’s normal to postpone sex until they’re really ready for it. Not only that, it’s normal not to be ready. And if you don’t talk to them about it, the conversation will be had by a peer who is less knowledgeable and less truthful.

But what about that porn? Never thought you would have a conversation with your kid about porn? The feeling is probably mutual. But here’s what he or she needs to know:

• Porn stars aren’t meant to look real. They’re flesh-and-blood cartoons. Many of those bodies are surgically exaggerated, and further exaggerated by the way they’re styled and photographed. No one should expect to look that way naturally.
• Porn sex isn’t real either — it’s fantasy. It’s the “fast food” version of sexuality. In the real world, people don’t relate to each other this way. They have complex needs, and sex is usually just one part of their relationship. Not only that, but when they do have sex, it doesn’t tend to look or sound like porn does.
• The unrealistic expectations and simplified sex in porn can be damaging to real relationships, especially if one partner is addicted to it. Real sex usually comes with real emotions — which are intentionally absent from porn.
• Young men who’ve become obsessed with online porn — which, after all, is available 24/7 — report having serious problems with their real romantic lives. Sexuality is mutable, and if what turns them on becomes very different from their real potential partners, they can find themselves in trouble — as can their partners.

Porn has become an insidious part of teenage culture, so it’s important to let your kids know that you are aware of that, and are comfortable talking about it. And when you do, it gives you the opportunity to share your values about when you think sex is appropriate.

These conversations, and it will take more than one, may be difficult to broach, but they get easier. And when your kids are faced with confusing, or even dangerous, situations, you want them to know they have an adult they can trust to turn to — you.

Related: I found porn on my 11-year-old’s phone. Should I talk to him?